This invention relates to punch retainers and release tools where the retainer is of the kind which employs a locking ball cooperating with a ball groove formed on the side wall of the shank of a punch, such as shown in U.S. Pat. No. 5,197,368 which issued Mar. 30, 1993, the disclosure of which is specifically incorporated herein by reference.
Metal punches are commonly retained in the body of a punch retainer by a diagonally movable locking ball. The locking ball is received in a diagonal ball hole and is spring biased into a seated position, in which a portion of the ball is partially received within a tapered ball groove or tear-drop shaped recess formed in the side wall of the shank of a punch. In removing the punch from the retainer, the locking ball is lifted out of its seated position against the bias of the spring, by a release tool. Formerly, a release tool had to be inserted through a small access opening in the lower face of the retainer body and an upward force on the release tool caused the ball to ride upwardly in its diagonal hole against a spring and out of locking engagement with the punch shank, thereby permitting the punch shank to be withdrawn.
In our patent '368, as identified above, embodiments are shown of arrangements by which a release tool may be inserted from a lateral position through an access slot in a side wall of the retainer. The access slot extends into the opening defined by the ball hole and a portion of the slot is below the lower circumference of the ball. The ball may be lifted by a tool from a seated position, by prying or by movement of the ball along a cam or inclined nose surface of the release tool.
Our patent '368 also describes the locking arrangement between the ball and the tear-drop shaped recess formed on a lateral side of the punch shank. The locking ball contacts the punch shank at two laterally spaced locations, while an opposite surface of the ball contacts the ball hole at a third location. In order to provide for access to the ball within the ball hole for lifting, it is important that the access slot be arranged and configured in such a manner that it does not intersect or interfere with either of the three ball contact locations.
Applicants' assignee, Dayton Progress Corporation, has for many years made and sold punch retainers of a unique and distinctive appearance in the form of a trilateral bodied retainer under the trademark True Position.RTM., the shape of which is also registered as U.S. Trademark Reg. No. 1,507,804. This retainer body incorporates a particularly compact arrangement of punch shank recess, locking ball hole, retainer body mounting holes, and dowel pin locating bores. The True Position.RTM. retainer has a pair of transversely positioned bolt holes, and also has a pair of dowel pin locating bores in addition to the ball hole and the punch shank receiving bore.
The grouping and number of such holes and bores through the body preclude the use of a ball release access slot of the kind which extends through the retainer body from one lateral side to the other, as shown in FIGS. 7, 8 and 11 of our patent '368. There is accordingly, a need for a ball lifting and retaining mechanism for punch retainers having a trilateral shaped retainer body.